1. Cellular Division

2. Cell Division All cells are derived from pre-existing cells
New cells are produced for growth and to replace damaged or old cells
Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals)

3. Keeping Cells Identical
The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules

4. Two new, identical DNA strands
DNA Replication
DNA must be copied or replicated before cell division
Each new cell will then have an identical copy of the DNA
Original DNA strand
Two new, identical DNA strands

5. Identical Daughter Cells
Two identical daughter cells
Parent Cell

6. Chromosomes

7. Prokaryotic Chromosome
The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

8. Eukaryotic Chromosomes
All eukaryotic cells store genetic information in chromosomes
Most eukaryotes have between 10 and 50 chromosomes in their body cells
Human body cells have 46 chromosomes or 23 identical pairs

9. Eukaryotic Chromosomes
Each chromosome is composed of a single, tightly coiled DNA molecule
Chromosomes can’t be seen when cells aren’t dividing and are called chromatin

10. Compacting DNA into Chromosomes
DNA is tightly coiled around proteins called histones

11. Chromosomes in Dividing Cells
Duplicated chromosomes are called chromatids & are held together by the centromere
Called Sister Chromatids

12. Karyotype
A picture of the chromosomes from a human cell arranged in pairs by size
First 22 pairs are called autosomes
Last pair are the sex chromosomes
XX female or XY male

13. The Y Chromosome Decides
Boy or Girl?
The Y Chromosome Decides
Y - Chromosome
X - Chromosome

14. Cell Reproduction

15. Types of Cell Reproduction
Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells
Mitosis & binary fission are examples of asexual reproduction
Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells
Meiosis is an example

16. Cell Division in Prokaryotes

17. Cell Division in Prokaryotes
Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission
Single chromosome makes a copy of itself
Cell wall forms between the chromosomes dividing the cell
Parent cell
Chromosome doubles
Cell splits
2 identical daughter cells

18. Prokaryotic Cell Undergoing Binary Fission

19. Animation of Binary Fission

20. The Cell Cycle

21. Five Phases of the Cell Cycle
G1 - primary growth phase
S – synthesis; DNA replicated
G2 - secondary growth phase
collectively these 3 stages are called interphase
M - mitosis
C - cytokinesis

22. Cell Cycle

23. Interphase - G1 Stage 1st growth stage after cell division
Cells mature by making more cytoplasm & organelles
Cell carries on its normal metabolic activities

24. Two identical copies of DNA
Interphase – S Stage
Synthesis stage
DNA is copied or replicated
Two identical copies of DNA
Original DNA

25. Interphase – G2 Stage 2nd Growth Stage
Occurs after DNA has been copied
All cell structures needed for division are made (e.g. centrioles)
Both organelles & proteins are synthesized

26. What’s Happening in Interphase?
What the cell looks like
Animal Cell
What’s occurring

27. Cells prepare for Division Cell Divides into Identical cells
Sketch the Cell Cycle
DNA Copied
Cells prepare for Division
Cells Mature
Daughter Cells
Cell Divides into Identical cells

28. Mitosis

29. Mitosis Division of the nucleus Also called karyokinesis
Only occurs in eukaryotes
Has four stages
Doesn’t occur in some cells such as brain cells

30. Four Mitotic Stages
Prophase
Metaphase
Anaphase
Telophase

31. Early Prophase
Chromatin in nucleus condenses to form visible chromosomes
Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal)
Cytoplasm
Nucleolus
Nuclear Membrane
Chromosomes

32. Late Prophase Nuclear membrane & nucleolus are broken down
Chromosomes continue condensing & are clearly visible
Spindle fibers called kinetochores attach to the centromere of each chromosome
Spindle finishes forming between the poles of the cell

33. Nucleus & Nucleolus have disintegrated
Late Prophase
Chromosomes
Nucleus & Nucleolus have disintegrated

34. Spindle Fiber attached to Chromosome
Kinetochore Fiber
Chromosome

35. What the cell looks like
Review of Prophase
What the cell looks like
What’s happening

36. Spindle Fibers
The mitotic spindle form from the microtubules in plants and centrioles in animal cells
Polar fibers extend from one pole of the cell to the opposite pole
Kinetochore fibers extend from the pole to the centromere of the chromosome to which they attach
Asters are short fibers radiating from centrioles

37. Sketch The Spindle

38. Metaphase
Chromosomes, attached to the kinetochore fibers, move to the center of the cell
Chromosomes are now lined up at the equator
Equator of Cell
Pole of the Cell

39. Metaphase Asters at the poles Spindle Fibers
Chromosomes lined at the Equator

40. Chromosomes at Equator
Metaphase
Aster
Chromosomes at Equator

41. What the cell looks like
Review of Metaphase
What the cell looks like
What’s occurring

42. Anaphase Occurs rapidly
Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers

43. Sister Chromatids being separated
Anaphase
Sister Chromatids being separated

44. What the cell looks like
Anaphase Review
What the cell looks like
What’s occurring

45. Telophase Sister chromatids at opposite poles Spindle disassembles
Nuclear envelope forms around each set of sister chromatids
Nucleolus reappears
CYTOKINESIS occurs
Chromosomes reappear as chromatin

46. Comparison of Anaphase & Telophase

47. Cytokinesis Means division of the cytoplasm
Division of cell into two, identical halves called daughter cells
In plant cells, cell plate forms at the equator to divide cell
In animal cells, cleavage furrow forms to split cell

48. Cleavage furrow in animal cell Cell plate in animal cell
Cytokinesis
Cleavage furrow in animal cell
Cell plate in animal cell

49. Mitotic Stages

50. Daughter Cells of Mitosis
Have the same number of chromosomes as each other and as the parent cell from which they were formed
Identical to each other, but smaller than parent cell
Must grow in size to become mature cells (G1 of Interphase)

51. Identical Daughter Cells
What is the 2n or diploid number? 2
Chromosome number the same, but cells smaller than parent cell

52. Review of Mitosis

53. Draw & Learn these Stages

54. Draw & Learn these Stages

55. Name the Mitotic Stages:
Interphase
Name this?
Prophase
Telophase
Name this?
Metaphase
Anaphase

56. Eukaryotic Cell Division
Used for growth and repair
Produce two new cells identical to the original cell
Cells are diploid (2n)
Chromosomes during Metaphase of mitosis
Cytokinesis
Anaphase
Prophase
Metaphase
Telophase

57. Name each stage as you see it occur?
Mitosis Animation
Name each stage as you see it occur?

58. Mitosis in Onion Root Tips
Do you see any stages of mitosis?

59. Test Yourself over Mitosis

60. Mitosis Quiz

61. Mitosis Quiz

62. Name the Stages of Mitosis:
Early prophase
Early Anaphase
Metaphase
Interphase
Early Telophase,
Begin cytokinesis
Late Prophase
Late telophase,
Advanced cytokinesis
Mid-Prophase
Late Anaphase

63. Early, Middle, & Late Prophase Telophase & Cytokinesis
Identify the Stages ?
Early, Middle, & Late Prophase ? ? ?
Metaphase
Anaphase
Late Prophase ? ? ?
Telophase & Cytokinesis
Late Anaphase
Telophase

64. Locate the Four Mitotic Stages in Plants
Anaphase
Telophase
Metaphase
Prophase

65. Uncontrolled Mitosis Cancer cells
If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors
Oncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell
Cancer cells

66. Meiosis Formation of Gametes (Eggs & Sperm)

67. Facts About Meiosis
Preceded by interphase which includes chromosome replication
Two meiotic divisions --- Meiosis I and Meiosis II
Called Reduction- division
Original cell is diploid (2n)
Four daughter cells produced that are monoploid (1n)

68. Facts About Meiosis
Daughter cells contain half the number of chromosomes as the original cell
Produces gametes (eggs & sperm)
Occurs in the testes in males (Spermatogenesis)
Occurs in the ovaries in females (Oogenesis)

69. More Meiosis Facts
Start with 46 double stranded chromosomes (2n)
After 1 division - 23 double stranded chromosomes (n)
After 2nd division - 23 single stranded chromosomes (n)
  Occurs in our germ cells that produce gametes

70. Why Do we Need Meiosis?
It is the fundamental basis of sexual reproduction
Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote

71. Fertilization – “Putting it all together”

72. Replication of Chromosomes
Replication is the process of duplicating a chromosome
Occurs prior to division
Replicated copies are called sister chromatids
Held together at centromere
Occurs in Interphase
Replication is the process of duplicating chromosome. The new copy of a chromosome is formed by DNA synthesis during S-phase. The chromosome copies are called sister chromatids. Sister chromatids are held together at the centromere.

73. A Replicated Chromosome
Gene X
Sister Chromatids
(same genes,
same alleles)
Homologs
(same genes, different alleles)
Homologs separate in meiosis I and therefore different alleles separate.

74. Meiosis Forms Haploid Gametes
Meiosis must reduce the chromosome number by half
Fertilization then restores the 2n number
from mom
from dad
child
too
much!
meiosis reduces
genetic content
The right number!

75. Meiosis: Two Part Cell Division
Sister
chromatids
separate
Meiosis I
Meiosis II
Homologs
separate
Diploid
Diploid
Haploid

76. Meiosis I: Reduction Division
Nucleus
Spindle
fibers
Nuclear
envelope
Early Prophase I
(Chromosome number doubled)
Late Prophase I
Metaphase I
Anaphase I
Telophase I (diploid)

77. Prophase I Late prophase Early prophase Chromosomes condense.
Spindle forms.
Nuclear envelope fragments.
Early prophase
Homologs pair.
Crossing over occurs.

78. Tetrads Form in Prophase I
Homologous chromosomes (each with sister chromatids)  
Join to form a TETRAD
Called Synapsis

79. Crossing-Over Homologous chromosomes in a tetrad cross over each other
Pieces of chromosomes or genes are exchanged
Produces Genetic recombination in the offspring

80. Homologous Chromosomes During Crossing-Over

81. Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment

82. Homologous pairs of chromosomes align along the equator of the cell
Metaphase I
Homologous pairs of chromosomes align along the equator of the cell

83. Anaphase I Homologs separate and move to opposite poles.
Sister chromatids remain
attached at their centromeres.

84. Telophase I Nuclear envelopes reassemble. Spindle disappears.
Cytokinesis divides cell into two.

85. Meiosis II Meiosis II produces gametes with
Only one homolog of each chromosome is present in the cell.
Gene X
Meiosis II produces gametes with
one copy of each chromosome and thus one copy of each gene.
Sister chromatids carry
identical genetic
information.

86. Meiosis II: Reducing Chromosome Number
Prophase II
Metaphase II
Telophase II
Anaphase II
4 Identical haploid cells

87. Prophase II
Nuclear envelope fragments.
Spindle forms.

88. Metaphase II
Chromosomes align
along equator of cell.

89. Anaphase II Sister chromatids separate and move to opposite poles.
Equator
Pole
Sister chromatids separate and move to opposite poles.

90. Telophase II Nuclear envelope assembles. Chromosomes decondense.
Spindle disappears.
Cytokinesis divides cell into two.

91. Results of Meiosis Gametes (egg & sperm) form
Four haploid cells with one copy of each chromosome
One allele of each gene
Different combinations of alleles for different genes along the chromosome

92. Oogenesis or Spermatogenesis
Gametogenesis
Oogenesis or Spermatogenesis

93. Spermatogenesis Occurs in the testes
Two divisions produce 4 spermatids
Spermatids mature into sperm
Men produce about 250,000,000 sperm per day

94. Spermatogenesis in the Testes
Spermatid

95. Spermatogenesis

96. Oogenesis Occurs in the ovaries
Two divisions produce 3 polar bodies that die and 1 egg
Polar bodies die because of unequal division of cytoplasm
Immature egg called oocyte
Starting at puberty, one oocyte matures into an ovum (egg) every 28 days

97. Oogenesis in the Ovaries

98. Oogenesis Oogonium (diploid) Mitosis Primary oocyte Meiosis I
Secondary
(haploid)
Meiosis II
(if fertilization
occurs)
First polar body
may divide
Polar
bodies
die
Ovum (egg)
Second
polar body a A X
Mature
egg

99. Comparing Mitosis and Meiosis

100. Comparison of Divisions
Mitosis
Meiosis
Number of divisions 1 2
Number of daughter cells 4
Genetically identical?
Yes No
Chromosome #
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Role
Growth and repair
Sexual reproduction